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Re: plpython3

From: James William Pye <lists(at)jwp(dot)name>
To: jd(at)commandprompt(dot)com
Cc: Greg Smith <greg(at)2ndquadrant(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Josh Berkus <josh(at)agliodbs(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: plpython3
Date: 2010-01-15 20:26:13
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Jan 14, 2010, at 2:03 PM, Joshua D. Drake wrote:
> What I would (as a non hacker) would look for is:
> (1) Generalized benchmarks between plpython(core) and plpython3u
> I know a lot of these are subjective, but it is still good to see if
> there are any curves or points that bring the performance of either to
> light.

I guess I could do some simple function I/O tests to identify invocation overhead(take a single parameter and return it). This should give a somewhat reasonable view of the trade-offs of "native typing" vs conversion performance-wise. One thing to keep in mind is that *three* tests would need to be done per parameter set:

 1. plpython's
 2. plpython3's (raw data objects/"native typing")
 3. plpython3's + @pytypes

The third should show degraded performance in comparison to plpythonu's whereas the second should show improvement or near equivalence.

@pytypes is actually implemented in pure-Python, so the impact should be quite visible.

I'm not sure there's anything else worth measuring. SRFs, maybe?

> (2) Example of the traceback facility, I know it is silly but I don't
> have time to actually download head, apply the patch and test this.

Well, if you ever do find some time, the *easiest* way would probably be to download a branch snapshot from;a=snapshot;h=refs/heads/plpython3;sf=tgz

It requires Python 3.1. 3.0 has been abandoned by

> This
> type of thing, showing debugging facilities within the function would be
> killer.

The test output has a *lot* of tracebacks, so I'll just copy and paste one here.

This one shows the traceback output of a chained exception.

-- suffocates a pg error, and attempts to enter a protected area
import Postgres

rp = Postgres.Type(Postgres.CONST['REGPROCEDUREOID'])

def main():
        fun = rp('nosuchfunc(int17,zzz)')
        # Should be valid, but the protection of
        # PL_DB_IN_ERROR should keep it from getting called.

SELECT pg_failure_suf_IFTE();
ERROR:  database action attempted while in failed transaction
CONTEXT:  [exception from Python]
Traceback (most recent call last):
   File "public.pg_failure_suf_ifte()", line 8, in main
    fun = rp('nosuchfunc(int17,zzz)')
 Postgres.Exception: type "int17" does not exist
CODE: 42704

During handling of the above exception, another exception occurred:

 Traceback (most recent call last):
   File "public.pg_failure_suf_ifte()", line 12, in main


> (3) A distinct real world comparison where the core plpython falls down
> (if it does) against the plpython3u implementation

Hrm. Are you looking for something that plpython3 can do that plpython can't? Or are you looking for something where plpython makes the user work a lot harder?

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